This proposal has two key objectives: 1) : To enhance career development for Dr. Badr as an independent investigator; 2) To provide protected time to allow Dr. Badr to mentor junior faculty and research fellows with the long term goal of reaching a critical mass of investigators in sleep research. This proposal covers two areas of current and future research: 1. To investigate the determinants of UA patency using fiberoptic imaging with special emphasis on REM sleep. 2) To investigate mechanisms of breathing instability during sleep and the interaction between ventilatory drive and UA patency. The current studies are concerned with long-term facilitation mechanisms which stabilize respiration after repeated perturbation. The proposed studies will be conducted in humans during natural sleep, subjects will span the spectrum at UA stability including normals, snorers and sleep apnea patients.